This invention relates generally to methods and apparatuses for analysis of vessel images, and more particularly to methods and apparatuses for assisting medical care personnel such as radiologists in preparing measurements and reports for surgical planning from images derived from computed tomographic, MR, and 3D radiation imaging.
In at least some computed tomography (CT) imaging system configurations, an x-ray source projects a fan-shaped beam which is collimated to lie within an X-Y plane of a Cartesian coordinate system and generally referred to as the xe2x80x9cimaging planexe2x80x9d. The x-ray beam passes through the object being imaged, such as a patient. The beam, after being attenuated by the object, impinges upon an array of radiation detectors. The intensity of the attenuated beam radiation received at the detector array is dependent upon the attenuation of the x-ray beam by the object. Each detector element of the array produces a separate electrical signal that is a measurement of the beam attenuation at the detector location. The attenuation measurements from all the detectors are acquired separately to produce a transmission profile.
In known third generation CT systems, the x-ray source and the detector array are rotated with a gantry within the imaging plane and around the object to be imaged so that the angle at which the x-ray beam intersects the object constantly changes. X-ray sources typically include x-ray tubes, which emit the x-ray beam at a focal spot. X-ray detectors typically include a collimator for collimating x-ray beams received at the detector, a scintillator adjacent the collimator, and photodetectors adjacent the scintillator.
An important application of computed tomographic (CT) imaging systems, as well as magnetic resonance (MR) imaging and 3-D x-ray (XR) imaging systems, is to produce 3D image data sets for vascular analysis, which can include analysis of a variety of tortuous tubular structures such as airways, ducts, nerves, blood vessels, etc. Production of such 3D image data sets is particularly important for radiologists, who are called upon to provide thorough visual reports to allow assessments of stenosis or aneurysm parameters, quantify lengths, section sizes, angles, and related parameters. Such information is commonly utilized by physicians to allow for surgical planning. For productivity reasons, as well as to reduce film costs, the 3D image data sets should be limited to only a small set of significant images.
3D visualization software provides a set of tools to perform length, angle or volume measurements and to visualize a volume in different ways, for example, using cross-sections, navigator or volume rendering. Known methods for quantification and analysis of vessel pathologies require an extensive array of tools to localize possible lesions, and then to perform measurements. Such methods are highly operator dependent, and require both time and software expertise. For example, a trained operator may need more than one hour to complete a single abdominal aorta aneurysm case. Even with trained operators given all the required time, results are not particularly reproducible and there are no consistent reporting frameworks. Furthermore, some measurements, such as true 3D-length measurement along vessels, cannot be performed using known manual tools. Because of these limitations, only a small number of sites are able to provide high-quality reports.
Analyzing tortuous structures, such as airways, vessels, ducts or nerves is one of the major applications of medical imaging systems. This task is accomplished today by using multiple oblique slices to analyze local segments of these structures. These views provide a clear, undistorted picture of short sections from these objects but rarely encompass their full length. Curved reformation images provide synthetic views that capture the whole length of these tubular objects and are therefore well suited to this analysis task. True 3D length measurements along the axis can be obtained from these views and they are not too far from the real anatomy in many cases. Curved reformation images can be generated by sampling values along a curve at equidistant points to generate lines, and then translating this curve by a sampling vector to generate the next image line.
Despite the ability to generate curved reformation images, there does not currently exist an interactive method of displaying such curved reformation images and quantitative information at the same time. That is, although geometrical features such as bifurcations, local stenoses, calcifications and other features of a vessel can be displayed, there does not currently exist a manner of simultaneously displaying, in a meaningful manner, those geometrical features along with various quantitative information about the vessels. Such quantitative information of interest can include, for example, the shapes of particular vessel sections and their cross-sectional areas, minimum diameters, maximum diameters, and other characteristics of the vessels.
Therefore, it would be advantageous if new methods and apparatuses were developed that allowed medical imaging systems and related 3D visualization software to generate vessel images that simultaneously provided visual, geometric characteristics of the vessels along with quantitative information of interest. It would further be advantageous if the vessel images were easy to interpret so that persons viewing the images could easily associate the particular quantitative characteristics of the vessels with actual positions along the vessels. It additionally would be advantageous if such vessel images could be displayed in an interactive manner to allow operators to obtain desired information in a simple, efficient, consistent, repeatable, and rapid manner.
The present invention is a method and apparatus for displaying tubular structures, and particularly a method and apparatus for displaying quantitative information about the tubular structures. According to the method, a polygon that approximates the centerline of the tubular structure of interest is defined by using automated methods that track this centerline or manually from user input. For each point of the centerline, a section of the structure of interest is defined in the plane orthogonal to the centerline, and for each section, information such as cross-sectional area, maximum diameter, and minimum diameter are calculated and stored in memory. For each point along the centerline, the cross-section that is normal to the centerline is found and aligned to a straight axis in order to obtain an unfolded image of the tubular structure. Then, along the side of the unfolded image of the tubular structure, a set of curves are displayed with the quantitative information previously stored. An index cursor is provided on the display. By moving this cursor, an operator can display the structure in other modes such as cross-section or navigator.
In particular, the present invention relates to a method of displaying information concerning a tubular structure. The method includes (a) determining a centerline along at least a portion of the tubular structure, and (b) determining a plurality of center points along the centerline, the center points being respectively separated from one another by a first sampling distance. The method further includes (c) determining a plurality of cross-sections at the plurality of center points, respectively, where each cross-section is perpendicular to the centerline at its respective center point, and (d) identifying first values associated with each of the cross-sections, where the first values are indicative of a first characteristic of the tubular structure at the respective cross-sections. The method additionally includes (e) generating a modified image of the tubular structure by computing a plurality of image lines of the modified image, where each image line corresponds to a respective cross-section, and (f) displaying a curve alongside the modified image, where the curve is representative of the first characteristic of the tubular structure, where the curve is formed by displaying a plurality of second values along a scale, where each second value is functionally related to a respective one of first values, and where each second value is positioned alongside the modified image of the tubular structure along a respective one of the image lines.
The present invention additionally relates to a method of displaying information concerning a tubular structure. The method includes (a) determining a centerline along at least a portion of the tubular structure, (b) determining a plurality of center points along the centerline, the center points being respectively separated from one another by a first sampling distance, and (c) determining a plurality of cross-sections centered on the plurality of center points, respectively, where each cross-section is perpendicular to the centerline at its respective center point. The method further includes (d) determining a plurality of segments within the plurality of cross-sections, respectively, and (e) determining a plurality of sets of segment points along the plurality of segments, respectively, where the segment points of each set are separated from one another by a second sampling distance. The method additionally includes (f) identifying first values at each of the cross-sections, where the first values are indicative of a first characteristic of the tubular structure at the respective cross-sections, and (g) generating a modified image of the tubular structure. The modified image is generated by determining a plurality of image lines of the modified image and a plurality of sets of image line points along the plurality of image lines, respectively, where each image line corresponds to a respective segment and each image line point corresponds to a respective segment point, and displaying at each image line point a color indicative of a second characteristic associated with its respective segment point. The method further includes (h) displaying a curve alongside the modified image, where the curve is representative of the first characteristic of the tubular structure, where the curve is formed by displaying a plurality of second values along a scale, where each second value is functionally related to a respective one of first values, and where each second value is positioned alongside the modified image of the tubular structure along a respective one of the image lines.
In particular, the present invention relates to a method of displaying information concerning a vessel. The method includes determining a centerline along at least a portion of the vessel, and determining a first pair of lines perpendicular to a pair of tangents of the centerline at a first pair of points along the centerline, respectively, where the first pair of points are spaced apart from one another along the centerline by a first distance. The method further includes identifying first characteristics associated with each of the first pair of lines, and generating an image of a modified vessel. The modified vessel has a straight axis with a second pair of points that are spaced apart from one another along the straight axis by a second distance. The modified vessel is generated to include second characteristics associated with a second pair of lines that are perpendicular to the straight axis at the second pair of points, respectively, where the second characteristics are related to the first characteristics.
The present invention further relates to an apparatus for displaying information concerning a vessel. The apparatus includes means for obtaining data concerning an actual vessel, and means for generating a modified vessel image based upon the obtained data, where the modified vessel image shows a straightened vessel having a first characteristic that is related to a second characteristic of the actual vessel as represented by the data. The apparatus further includes means for generating, alongside the modified vessel image, a graphical image showing variation of a parameter of the actual vessel as a function of position along the modified vessel image.